Electronic element

ABSTRACT

The object is to fabricate a novel organic semiconductor element which can effectively utilize the main-chain conduction of a conjugated high molecular compound having semiconductor-like properties. Provided is an electronic element which contains, as components, a pair of electrodes which is formed on a substrate, a mesoporous film in which tubular mesopores, which are orientation controlled in one direction, are formed, the mesoporous film being formed between the electrodes so as to be in contact with the electrodes, a conjugated high molecular compound held in the tubular mesopores, and a third electrode which is electrically insulated from the conjugated high molecular compound and is in contact with the mesoporous film.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electronic element and,particularly, to a novel organic semiconductor element which uses aconjugated high molecular compound, more particularly, to a field-effecttransistor which uses an organic semiconductor.

More specifically, the invention relates to an electronic device whichutilizes the main-chain conduction of a conjugated high molecularcompound which is orientation controlled at a molecular level.

2. Related Background Art

Organic semiconductors have various possibilities, such as therealization of low cost processes and flexible devices, and recent yearshave seen very active research and development aimed at the applicationof electronic devices, such as electroluminescence elements andfield-effect transistors (FETs).

Organic semiconductors used in electronic devices are broadly dividedinto low molecular compounds and high molecular compounds.

For example, complexes, such as copper and phtalocyanine, and polycyclicorganic compounds, such as pentacene, are used as low molecularcompounds, and thin film designs are obtained by techniques such asevaporation, whereby devices are fabricated.

In contrast to low molecular compounds, high molecular compounds have astructure in which conjugated double bonds are continuous as inpolythiophene, polypyrrole, polyacetylene and the like, and they areused in fabricating devices by techniques such as printing.

In the case of low molecular compounds, almost all molecules have astructure in which the molecules are stacked due to interactions by Πelectrons, and carriers migrate by hopping conduction among themolecules.

In many cases, in-plane orientation directions are at random. However,it has been reported that anisotropy in electrical conductivity can beobserved by arraying molecules in a specific direction.

A technique which has accomplished an improvement in the characteristicsof an FET by orienting low molecular compounds is disclosed in theJapanese Patent Application Laid-Open No. H07-206599, for example.

In conjugated high molecular compounds, ideally, Π electrons aredelocalized throughout the molecules, and hence conjugated highmolecular compounds have high carrier mobility within the molecules.

Among polymer chains, carriers migrate by hopping conduction.

At present, almost all polymer chains are used in a random condition inwhich they are not orientation controlled, and hopping conduction is amain conduction mechanism.

However, even in hopping conduction, it is possible to increase carriermobility by aligning the orientation direction of molecules, and theJapanese Patent Application Laid-Open No. H09-246921 discloses astructure in which fibrils with aligned directions of polymer chains areformed so as to be orthogonal to the direction of an electrode.

Also, there have been proposed several techniques which involveproviding protection from deterioration reactions and the like byintroducing a conjugated high molecular compound as a guest into aninorganic or organic host material.

The object of these techniques is to prevent the attack of highmolecular compounds by oxygen, water and the like.

A technique which uses cyclodextrin as a host material is disclosed inthe Japanese Patent Application Laid-Open No. 2003-298067.

There are also several reports on techniques for introducing aconjugated high molecular compound into the pores of mesoporous silica.

In “Science,” Vol. 288, p. 652, there is a report to the effect thatpoly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinnylene](abbreviated as MEH-PPV), which is a conjugated polymer, is introducedin the mesopores of mesoporous silica monolith for which the orientationdirection is controlled by the application of a ferromagnetic field.

However, the above-described techniques had several problems asdescribed below.

That is, in the case of the method described in Non-patent Document 1,the mesoporous silica monolith contains many fine cracks and itsapplication to electronic elements was difficult.

Also, the shown orientation distribution of pores was wide and it couldnot be said that the orientation controllability is high. Furthermore,the form of a monolith was not suitable for the fabrication of devices.

SUMMARY OF THE INVENTION

Against the above-described technical background, the present inventionhas been made in view of the above-described problems, and the inventioncan fabricate, by a simple process, a novel high-performance electronicelement in which by forming a conjugated high molecular compound in ahighly anisotropic space of an oriented mesoporous film, the directionof polymer chains is controlled on a macroscopic scale and high carriermobility by main-chain conduction is utilized.

According to an aspect of the present invention, there is provided anelectronic element, comprising:

a pair of electrodes formed on a substrate;

a mesoporous film having tubular mesopores oriented in one direction,the mesoporous film being formed between the pair of electrodes so as tobe in contact with the pair of electrodes;

a conjugated high molecular compound held in the tubular mesopores; and

a third electrode which is electrically insulated from the conjugatedhigh molecular compound and formed so as to be in contact with themesoporous film.

The orientation direction of the tubular mesopores is preferablyparallel to the direction of an electric field when an electricalpotential is applied across the pair of electrodes.

The electronic element is preferably a field-effect transistor whichcontrols the amount of a current flowing across the pair of electrodesby an electrical potential applied to the third electrode. In theelectronic element, a material for the mesoporous film is preferablysilica. Alternatively, in the electronic element, a material for themesoporous film is preferably a hybrid material of silica and an organicsubstance.

In the electronic element, a material for the mesoporous film preferablycontains a silicon oxide.

In the electronic element, at least a portion of the substrate ispreferably a substrate having electrical conductivity and the substrateserves also as the third electrode.

According to another aspect of the present invention, there is provideda method of manufacturing the electronic element, wherein a step offorming a conjugated high molecular compound in tubular mesopores whichare orientation controlled comprises:

a step of forming a mesoporous film which is made up so as to containtubular molecular assemblies of a surfactant having a uniform diameter,which are oriented in one direction;

a step of removing the surfactant from the pores of the mesoporous film;

a step of performing treatment so that pore surfaces of the mesoporousfilm after removal of the surfactant obtain hydrophobicity; and

a step of introducing the conjugated high molecular compoundsubsequently to the hydrophobicizing treatment.

According to still another aspect of the present invention, there isprovided a method of manufacturing the electronic element, wherein astep of forming a conjugated high molecular compound in tubularmesopores which are orientation controlled comprises:

a step of forming a mesoporous film which is made up so as to containtubular molecular assemblies of a surfactant having a uniform diameter,which are aligned in one direction, by use of a surfactant having afunctional group capable of forming a conjugated high molecular compoundby polymerization; and

a step of forming a conjugated high molecular compound by causing asurfactant in the mesoporous film to polymerize.

According to a further aspect of the present invention, there isprovided a method of manufacturing an electronic element, comprising:

a step of forming a mesoporous film having tubular mesopores, which areorientation controlled in one direction, on a substrate;

a step of forming a conjugated high molecular compound in theorientation controlled tubular mesopores;

a step of forming a pair of electrodes for forming an electric fieldparallel to the direction of the pores so as to be in contact with themesoporous film having tubular mesopores in which a conjugated highmolecular compound is formed; and

a step of forming a third electrode which is electrically insulated fromthe conjugated high molecular compound and is in contact with themesoporous film.

According to a further aspect of the present invention, there isprovided a method of manufacturing an electronic element, comprising:

a step of preparing a substrate which has an electrically conductivepart in at least a portion of a surface thereof;

a step of forming a mesoporous film having tubular mesopores, which areorientation controlled in one direction, on the electrically conductivepart of the substrate;

a step of forming a conjugated high molecular compound in the tubularmesopores, which are orientation controlled; and

a step of forming a pair of electrodes for forming an electric fieldparallel to the direction of the pores so as to be in contact with themesoporous film having tubular mesopores in which a conjugated highmolecular compound is formed.

According to the present invention, it is possible to fabricate a novelorganic semiconductor element in which by the orientation control of aconjugated high molecular compound in an oriented nanospace ofmesoporous silica, the main-chain conduction of the conjugated highmolecular compound having semiconductor-like properties.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram to explain a preferred mode of anelectronic element of the present invention;

FIG. 2 is a schematic diagram to explain another preferred mode of anelectronic element of the present invention;

FIG. 3 is a schematic diagram of a reaction vessel to prepare amesoporous film by the nonuniform nucleation-nucleus growth method;

FIG. 4 is a schematic diagram of a film forming device which is used inthe dip coating method among methods of preparing a mesoporous film bythe solvent evaporation method;

FIGS. 5A, 5B, 5C, 5D and SE are schematic diagrams to explain afabrication process of an element in Embodiment 1 of the presentinvention;

FIGS. 6A, 6B, 6C, 6D, 6E and 6F are schematic diagrams to explain afabrication process of an element in Embodiment 2 of the presentinvention; and

FIGS. 7A and 7B are schematic diagrams which respectively show amesoporous silica film having oriented conjugated polymer chains withinpores, which is prepared by using a surfactant having a polymerizingpart, in Embodiment 3 of the present invention, and a partially enlargedportion of the mesoporous silica film.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Most preferred modes for carrying out the present invention will bedescribed below by referring to the accompanying drawings.

FIG. 1 is a diagram which schematically shows a preferred mode of anelectronic element of the present invention.

In FIG. 1, the reference numeral 11 denotes a substrate havingelectrical conductivity on its surface, the reference numeral 12 denotesan insulating film, the reference numeral 13 denotes an electrode(source), the reference numeral 14 denotes an electrode (drain), thereference numeral 15 denotes a mesoporous film, and the referencenumeral 16 denotes a tubular mesopore holding a conjugated highmolecular compound.

FIG. 1 shows a structure in which the substrate surface has electricalconductivity and functions as a gate electrode. However, in anelectronic element of the present invention, as shown in FIG. 2, thestructure may be such that a gate electrode is formed on a mesoporousfilm, which is formed on an insulating substrate and carries conjugatedpolymers.

The gate electrode may be formed in such a manner as to surround thefilm.

The greatest feature of the present invention resides in that tubularmesopores having a uniform diameter are orientation controlled in onedirection in the plane of a mesoporous film, and that conjugatedpolymers having semiconductor-like properties are orientationcontrolled, with the molecular chains aligned in the direction of pores,in a highly anisotropic nanospace having the orientation.

An electronic element of the structure shown in FIG. 1 will be describedin the order according to a procedure for manufacturing the element.

In the manufacture of an element of the present invention, first, amesoporous film having oriented tubular mesopores is prepared on asubstrate.

First, the mesoporous film will be described.

Pores of the mesoporous film of the present invention are formed by themolecular assemblies of a surfactant (micelles), and pores of the samediameter are formed because the number of associations forming micellesis the same under some conditions.

Although various configurations, such those of a sphere, a tube andlayer, are known as the shapes of micelles, the shape of the micelleswhich form a mesoporous film related to the present invention isbasically tubular.

The mesopores mentioned in the present invention refer to pores havingdiameters in the range of 2 nm to 50 nm, according to the definition byIUPAC.

In a mesoporous silica film of the present invention, pores have asubstantially uniform diameter.

The pores of uniform diameter mentioned here suggest that the poredistribution found by a technique for calculating pore diameter from theresults of a measurement of nitrogen gas adsorption has a single maximumvalue, and that in this pore diameter distribution, not less than 60% ofpores are included in a range having a width of 10 nm.

The pore diameter distribution is calculated by analytic methods, suchas the Barrett-Joyner-Halenda (BJH) method, from an obtained isothermaladsorption curve.

A range having a width of 10 nm is a range of width in which thedifference between a minimum value and a maximum value is 10 nm, as inthe case of 2 nm to 12 nm, for example.

As used herein, the term “mesoporous film” refers to a mesoporous filmwhich has hollow pores. In the present invention, however, this term isused as a term including a mesoporous film having a structure in whichan organic guest species, a surfactant and the like are held withinpores.

A mesoporous film of the present invention may have the structuralfeature that tubular mesopores are orientation controlled in onedirection and that as will be described later, conjugated polymer chainsbe held in the nanospace of the mesoporous film.

Materials containing silicon oxides are preferably used as materials forforming pore walls of a porous material.

Particularly, silica or hybrid materials of silica and organicsubstances are particularly preferably used.

“Hybrid” here is not at least a mixture and refers to a hybrid compoundmaterial in which inorganic components and organic components are bondedby covalent bonds, for example, as in O—Si—C—Si—O.

In a mesoporous film of the present invention, the orientation directionof pores in the plane is specified in one direction by the structuralanisotropy of the surface of a substrate.

The structural anisotropy of the surface of a substrate refers to, forexample, the anisotropy of the atomic arrangement on a specific crystalplane on a crystalline substrate, the anisotropy of an irregularstructure formed on a substrate, the structural anisotropy within a highmolecular compound film formed on a substrate and the like.

In the case shown in FIG. 1 where a substrate serves also as a gateelectrode, it is necessary that an appropriate part of the substratehave electrical conductivity. Basically, however, any substrate can beused.

In the case of the structure shown in FIG. 2, the selection range ofsubstrates is wider.

Substrates applicable to the present invention will be described infurther detail.

First, a crystalline substrate having anisotropy in the atomicarrangement on the surface will be described.

As a crystal plane having anisotropy in the atomic arrangement on thesurface, for example, the (110) plane of a single crystal substratehaving a crystal structure which is the diamond structure or a singlecrystal substrate having a crystal structure which is the zinc-blendtype structure is preferably used, and particularly, the (110) plane ofsilicon is preferably used.

Because on these surfaces a specific orientation direction of atoms isuniquely determined, these surfaces have the capacity to orientsurfactant assemblies.

The orientation control of pores of a silica mesostructure obtained byusing a substrate in which the atomic arrangement on the surface hasdouble symmetry, such as the (110) plane of silicon single crystal, hasbeen discovered by the present inventors and described in the JapanesePatent Application Laid-Open No. 2000-233995.

In using these substrates, it is necessary that a clean crystal surfacebe exposed.

For example, in the case of a silicon substrate, it is necessary toremove a natural oxide film present on the surface.

The purpose is relatively simple to accomplish in a simple process, suchas treating the surface in dilute hydrofluoric acid for several minutes.

For example, the (110) plane of a highly doped silicon single crystalhas sufficiently low resistance, ant it is easy to impart the functionof a gate electrode to this surface.

Next, a description will be given of a substrate on which a highmolecular compound film having structural anisotropy is formed.

The Langmuir-Blodgett method and the rubbing method will be describedhere. However, techniques other than these methods can be used so longas they can form a high molecular compound having structural anisotropyon a substrate.

These methods have universality, because in a case where this highmolecular compound film having structural anisotropy is to be formed,these methods can make similar surface conditions even when any materialis used as a substrate to be used in the front-end.

When the function of a gate electrode is imparted to a substrate asshown in FIG. 1, a highly doped silicon wafer, a glass substrate onwhich a metal of low activity such as gold is evaporated, etc. can beused as a substrate on which a polymer film is formed.

First, the Langmuir-Blodgett method, i.e., a method by which aLangmuir-Blodgett film (an LB film) of a high molecular compound isformed will be described.

An LB film is a film which is obtained by transferring a monomolecularfilm developed on a water surface onto a substrate, and it is possibleto form a film of a desired number of layers by repeating filmformation.

The LB film mentioned in the present invention includes a monomolecularcumulative film of LB film derivatives, the chemical structure of whichis changed, with a cumulative structure maintained, by subjecting an LBfilm formed on a substrate to treatment, such as heat treatment.

For example, a polyimide LB film can be prepared by developing analkylamine salt of polyamic acid on a water surface, laminating films bythe LB method and then performing heating.

It has been made clear by an infrared absorption analysis and the likethat in a polyimide LB film thus prepared, polymer chains are orientedparallel to the drawing-up direction of the substrate during LB filmpreparation.

Because of this structural anisotropy of the polymer film of thesubstrate surface, the substrate on which the LB film of a highmolecular compound ensures that the tubular mesopores of a mesoporousfilm formed on the substrate can be orientation controlled in onedirection.

This technique has been discovered also by the present inventors anddescribed in the Japanese Patent Application Laid-Open No. 2001-058812.

Subsequently, a description will be given of a substrate on which a highmolecular compound film subjected to rubbing treatment is formed.

This substrate on which a high molecular compound film subjected torubbing treatment is preferably used in preparing a mesoporous filmhaving oriented tubular mesopores used in the present invention.

In rubbing treatment, a substrate is coated with a polymer by techniquessuch as spin coating and this coated substrate is rubbed with a clothand the like in one direction.

A rubbing cloth is wound around a roller, and the roller which isrotating is brought into contact with the substrate surface and rubbingis performed by moving a stage to which the substrate is fixed in onedirection with respect to the roller.

A rubbing cloth most suited to a polymer material which is used isselected. However, general cloths of nylon, rayon and the like can beused.

The rubbing strength is optimized by parameters, such as the number ofrevolutions of a roller, the strength with which the roller is pressedagainst a substrate, and the moving speed of a stage to which thesubstrate is fixed.

For a high molecular compound which is subjected to rubbing treatment,basically, materials are not limited so long as they can withstand aforming process of a mesostructure film, which will be described layer,and permit the orientation control of pores in the mesostructure.Polyimide and the like are preferably used.

Two types of structural anisotropies are induced by rubbing treatment ina high molecular compound film on the substrate surface.

In one type, by strongly rubbing the surface of a polymer film with acloth, fine irregularities are formed on the surface. This irregularstructure has high anisotropy because the surface is rubbed in onedirection by use of a roller.

In another type, a polymer compound is elongated while being heated bythe heat generated during rubbing treatment to above its glasstransition point. This causes the sequence anisotropy of polymer chains.

The present inventors consider that the former type is induced in almostall high molecular compound films by rubbing treatment, whereas thelatter type is induced under some conditions from a relativerelationship between the physical properties based on the structure ofpolymer chains and rubbing conditions.

Also in this substrate subjected to rubbing treatment, because of theanisotropy of the structure of the surface, it is possible to performthe orientation control of the tubular mesopores in a mesoporous silicafilm formed on the substrate in one direction.

Also this technique has been discovered by the present inventors anddescribed similarly in the Japanese Patent Application Laid-Open No.2001-058812.

Next, methods of preparing a thin film of a mesostructure on a substratewill be described.

Methods of preparing a mesostructure film on a substrate are broadlydivided into two methods.

One is based on nonuniform nucleation-nucleus growth from the inside ofa solution to the surface of a substrate, and the other is a methodcalled a solvent evaporation method based on the sol-gel method.

The former is described, for example, in “Chemistry of Material,” Vol.14, pp. 766-772, and the latter is described, for example, in “Nature,”Vol. 389, pp. 364-368.

First, a description will be given of a method based on nonuniformnucleation-nucleus growth from the inside of a solution to the surfaceof a substrate.

This method is mainly used in the preparation of a mesoporous silicafilm, and a thin film of a mesostructure is prepared by using a methodsimilar to crystal growth.

Under this method, by holding the above-described substrate in aprecursor solution, which is obtained by adding a substance whichbecomes a raw material for the aimed pore wall forming material, to anaqueous solution of a surfactant, a mesoporous film is formed on thesubstrate.

A reaction vessel used in the formation of a mesostructure film by thismethod has a construction as shown in FIG. 3, for example.

Materials for the reaction vessel 31 are not especially limited so longas they have no effect on reactions, and materials such as polypropyleneand Teflon (registered trademark) can be used.

In order that the reaction vessel is not broken under pressure duringreactions, the reaction vessel may sometimes be further contained in aclosed vessel made of a material of high rigidity, such as stainlesssteel.

In the reaction vessel, a substrate holder 33 is placed as shown in FIG.3, for example, and a substrate 35 is held by using this holder.

During reactions, the formation of a mesostructure occurs not only onthe substrate, but also in the solution. Therefore, precipitates in thesolution accumulate on the substrate.

In order to prevent this, during reactions the substrate is held in thesolution, with its surface on which a film is formed faced downward.

The reaction solution is a solution which contains a surfactant and asubstance which becomes a raw material for the aimed inorganic material,such as alkoxide.

According to the material which forms pore walls, an appropriate amountof an acid or the like, which is a hydrolysis reaction catalyst of rawmaterials for inorganic components, may sometimes be added.

When alkoxide is used, those in which alcohols formed as a result ofhydrolysis are soluble in water are preferably used.

For example, when pore walls are made of silica, the reaction solutionis adjusted by adding tetraethoxysilane or tetramethoxysilane to anacidic aqueous solution of a surfactant.

A surfactant to be used is appropriately selected according to a methodof introducing a conjugated high molecular compound into pores.

As will be described later in detail, when a method of introducing aconjugated high molecular compound into hollow pores after the removalof a surfactant in the pores is adopted, it is possible to use a broadrange of surfactants, such as a cationic surfactant, for example,quaternary alkyl ammonium, and a nonionic surfactant containingpolyethylene oxide as a hydrophilic group, and surfactants are notespecially limited.

The length of the molecules of the surfactant to be used is determinedaccording to the pore diameter of the aimed mesostructure, and additivessuch as mesitylene may be added in order to increase the diameter of thesurfactant micelles.

On the other hand, in a case where a conjugated high molecular compoundis formed by directly performing a polymerizing reaction by use of asurfactant having a polymerizing part, a surfactant which has apolymerizing part, a suitable hydrophoric group and a suitablehydrophilic group is used after it is designed and synthesized to suitthe aimed pore structure.

Also in the latter case, it is possible to make a wide selection ofstructures of a polymerizing part and structures of a hydrophilic groupwhich are to be used.

For the acid to be used, it is possible to use general acids, such ashydrochloric acid and nitric acid.

The shape and structure of a film which precipitates on a substrate arenot only greatly affected by the concentrations of a surfactant, an acidand raw materials for inorganic components, but also influenced by theproperties of the substrate surface.

Therefore, it is necessary to perform film formation by optimizing thecomposition of a reaction solution according to the substrate to beused.

Under such conditions a mesoporous material can be deposited on thesubstrate.

Temperatures at which a mesoporous material is deposited are notespecially restricted, and they are selected in the temperature range ofroom temperature to 100° C. or so.

The reaction time is several hours to several months, and there is atendency that the longer the time, the larger the thickness of amesoporous film which is obtained.

A mesoporous film thus formed on the substrate is naturally dries in theair after it is cleaned with pure water, whereby a final film isobtained.

By removing surfactant micelles of a template from a mesoporous filmfabricated as described above, it is possible to prepare a mesoporousfilm having hollow pores.

General methods can be used to remove a surfactant, and are selectedfrom among baking, oxidation and decomposition by ozone formed byirradiation with ultraviolet light, extraction by a solvent, extractionby a fluid in a supercritical condition and the like.

For example, in the case of mesoporous silica, it is possible tocompletely remove a surfactant with hardly destructing the mesostructureby baking mesoporous silica in the air at 550° C. for ten hours.

It is preferred that the baking temperature and time be optimized by amaterial which forms pore walls and a surfactant which is used.

When a high molecular compound is prepared on the surface of a substratein order to perform the orientation control of pores, a polymer film fororientation control which is present between a mesoporous film and thesubstrate is also removed by baking, with the result that the structureis such that the mesoporous film which has been orientation controlledis formed directly on the substrate.

When means of extraction by a solvent and the like are used, it ispossible to form a mesoporous film on a substrate of a material whichcannot withstand baking although 100% removal of a surfactant isdifficult.

The removal of a surfactant is a step which is necessary only when aconjugated high molecular compound is introduced into pores after theremoval of a surfactant from the pores, and this step is of courseunnecessary when a mesoporous film is prepared by using a polymerizingsurfactant, which is polymerized in pores.

Next, a film formation by the solvent evaporation method will bedescribed.

In the solvent evaporation method, an aqueous solution, an organicsolution or an organic solvent/water mixed solution, which contains asurfactant having concentrations which are not more than a criticalmicelle concentration and a precursor of an inorganic substance formingpore walls, is applied to a substrate by spin coating, dip coating, mistcoating and the like. A mesostructure is formed with an increase in theconcentration of the surfactant due to the drying of the solvent duringcoating.

Alcohols and the like are used as the organic solvent.

This method has the advantages that constraints to substrate materialsare small because of relatively gentle reaction conditions, that thefilm preparation in a short time is possible and the like.

As a device for performing spin coating and dip coating, general onescan be used and there is no restriction. In some cases, however, meansfor controlling the temperature of a solution, means for controlling thetemperature and humidity at which coating is performed may be provided.

A description will be given of a method of preparing a mesoporous filmby use of dip coating, for example.

An example of a device used in dip coating is schematically shown inFIG. 4.

In FIG. 4, the reference numeral 41 denotes a vessel, the referencenumeral 42 denotes a substrate, and the reference numeral 43 denotes aprecursor solution.

The precursor solution 43 is an aqueous solution, an organic solution ora mixed solution of an organic solution and water, which contains asurfactant having concentrations which are not more than a criticalmicelle concentration and a precursor of inorganic components, and insome cases, an acid or the like which acts as a hydrolysis andpolycondensation catalyst may be added.

For example, a solution which is used in preparing mesoporous silicafilm, is obtained by dissolving a surfactant in an alcohol/water mixedsolvent and adding an acid which is a hydrolysis catalyst to thesolvent.

As in the preparation method by nonuniform nucleation-nucleus growth, asurfactant to be used is appropriately selected according to a method ofintroducing a conjugated high molecular compound into pores.

As will be described later in detail, when a method of introducing aconjugated high molecular compound into hollow pores after the removalof a surfactant in the pores is adopted, it is possible to use a broadrange of surfactants, such as a cationic surfactant, for example,quaternary alkyl ammonium, and a nonionic surfactant containingpolyethylene oxide as a hydrophilic group, and surfactants are notespecially limited.

The length of the molecules of the surfactant to be used is determinedaccording to the pore diameter of the aimed mesostructure, and additivessuch as mesitylene may be added in order to increase the diameter of thesurfactant micelles.

On the other hand, in a case where a conjugated high molecular compoundis formed by directly performing a polymerizing reaction by use of asurfactant having a polymerizing part, a surfactant which has apolymerizing part, a suitable hydrophoric group and a suitablehydrophilic group is used after it is designed and synthesized to suitthe aimed pore structure.

Also in the latter case, it is possible to make a wide selection ofstructures of a polymerizing part and structures of a hydrophilic groupwhich are to be used.

For the acid to be used, it is possible to use general acids, such ashydrochloric acid and nitric acid.

The substrate 42 on which a mesoporous film is to be prepared is fixedto a rod 45 by use of a holder 44 and moved up and down by use of az-stage 46.

During film formation, the reaction solution 43 is controlled to adesired temperature by using a heater 48 and a thermocouple 47 asrequired.

In order to improve the controllability of the solution temperature, thewhole vessel may sometimes be put in a heat insulating vessel which isnot shown in the figure.

It is preferred that the substrate to which the reaction solution hasbeen applied be dried in a device which permits the control oftemperature and humidity.

Aging may sometimes be performed in a high humidity atmosphere after thedrying step.

In addition to dip coating and spin coating, the pen-lithography methodand the ink jet method described in “Nature,” Vol. 405, p. 56 are alsoeffective methods of preparing a mesoporous film based on the solventevaporation method.

If these methods are used, it is possible to pattern a mesoporous filmin desired places on a substrate.

In the pen-lithography method, a reaction solution is used as if it wereink, and the solution is applied from a pen tip to draw lines. Bychanging the pen shape, the moving speed of the pen and substrate, thefluid supply speed to the pen and the like, it is possible to freelychange the line width and at present, it is possible to draw with linewidths from the order of μm to the order of mm.

It is possible to draw arbitrary patterns of straight lines, curvedlines and the like, planar patterning is also possible if it is ensuredthat the spreads of the reaction solution applied to the substrateoverlap each other.

When discontinuous dot-like patterns are to be drawn, the ink jet methodis more effective.

In this method, a reaction solution is used as if it were ink, and agiven amount of the solution is discharged as liquid drops from an inkjet nozzle and applied.

If the reaction solution is applied in such a manner that the spreads ofthe reaction solution which reaches the substrate overlap each other,both linear patterning and planar patterning are possible.

Also in the case of a mesostructure film prepared by this solventevaporation method, in the same manner as with a film prepared bynonuniform nucleation-nucleus growth, it is possible to prepare amesoporous film having hollow pores by removing a surfactant from insidepores.

The removal of a surfactant is a step which is necessary only when aconjugated high molecular compound is introduced into pores after theremoval of a surfactant from the pores, and this step is of courseunnecessary when a mesoporous film is prepared by using a polymerizingsurfactant, which is polymerized in pores.

When the formation of a mesoporous film is performed by theabove-described methods by use of a substrate having structuralanisotropy on the surface as described above, it is possible to form anoriented mesoporous film in which the direction of pores is controlledin one direction by the anisotropy of the substrate.

The pore structure of a mesoporous film of the present invention can beevaluated under a transmission electron microscope and by an X-raydiffraction analysis.

However, in the case of a mesoporous film of the present invention,tubular mesopores are formed parallel to the substrate and, therefore,it is necessary to use an in-plane X-ray diffraction analysis whenorientations in the plane are to be evaluated.

When a mesoporous film having uniaxially-oriented tubular mesopores ofthe present invention is evaluated by in-plane X-ray diffraction, twodiffraction peaks are observed at intervals of 180° in an in-planerocking curve.

In a mesoporous film of the present invention, the orientation directionof pores is governed by the direction of anisotropy of a substrate, andthe pores are often oriented, for example, in a direction perpendicularto the direction of rubbing treatment or the drawing-up direction of thesubstrate during LB film formation.

However, in some structures of a high molecular compound on thesubstrate or in some surfactants to be used, the pores may be orientedin a direction reverse to this direction, i.e., in a direction parallelto the direction of rubbing treatment or the drawing-up direction of thesubstrate during LB film formation.

A mesoporous film prepared in the present invention is characterized byhaving substantially uniform mesopores.

The size of pores and pore diameter distribution can be found frommeasurement results of an isothermal adsorption curve of nitrogen gasand the like.

In a mesoporous film of the present invention, the pore diameterdistribution found from measurement results of an isothermal adsorptioncurve of nitrogen gas and the like by the Barrett-Joyner-Halenda (BJH)method has a single peak in the range of 2 nm to 50 nm, and in the foundpore diameter distribution, not less than 60% of pores are included in apore diameter range having a width of 10 nm.

As materials for pore walls of a mesoporous film used in the presentinvention, those containing oxides of silicon are preferably used.

Furthermore, silica and hybrid materials of silica and organicsubstances are preferably used.

Subsequently, a description will be given of methods of fabricating astructure in which a conjugated high molecular compound is held in poresof a mesoporous silica film prepared as described above.

The methods are broadly divided into two categories as will be describedbelow.

However, methods other than these can be applied so long as they canform a structure in which a conjugated high molecular compound is heldin pores.

For example, there is a method by which after a catalyst is carriedwithin pores, a conjugated high molecular compound is polymerized in thepores.

In the first method, by causing heat or a polymerization initiator toact on a mesoporous film having uniaxially-oriented mesopores fabricatedby use of a surfactant having a polymerizing part, a structure in whichthe surfactant is polymerized is made.

An optimum polymerization method is selected according to a polymerizingpart of a surfactant to be used.

The polymerizing part of a surfactant used in this case is notespecially restricted so long as it forms conjugated polymer chains bypolymerization, and a diacethylene part, a pyrrole part, a thiophenepart and the like can be enumerated as examples. However, thepolymerizing part is not limited to them.

The hydrophilic group part is not especially restricted, and forexample, a quaternary alkyl ammonium part, a polyethylene oxide part andthe like can be used. However, the hydrophilic group part is not limitedto them.

Generally, an alkyl group is used in the hydrophoric group.

In this method, a conjugated high molecular compound is immediatelyformed in pores by performing a polymerization reaction by use of anoptimum technique.

In the second method, a mesoporous silica film havinguniaxially-oriented tubular mesopores is prepared by use of a generalsurfactant and a conjugated high molecular compound is introduced intohollow mesopores of the mesoporous silica film formed by removing thesurfactant from the pores.

For an example in which a conjugated polymer is introduced into pores ofa mesoporous silica film, in which the orientation direction in theplane is controlled in one direction, there is a study by the presentinventors, the contents of which are described in “Journal of theAmerican Chemical Society,” Vol. 126, pp. 4476-4477.

In this study, it is clearly shown that conjugated polymer chains arehighly orientation controlled by introducing a conjugated high molecularcompound into mesopores, which are controlled in one direction.

When a conjugated high molecular compound is introduced by this method,it is preferred that first, the inner surfaces of pores are subjected tohydrophobicizing treatment.

By making the interior of pores hydrophobic, the introduction of aconjugated high molecular compound into pores tends to become remarkablyimproved.

For example, by treating a film with phenyldimethyl-chlorosilane or1,1,1,3,3,3-hexamethyl-disilazan, an organic substance is bonded to asilanol group in pores, whereby it is possible to efficientlyhydrophobicize the interior of the pores.

However, substances used for the hydrophobicizing treatment of theinterior of pores are not limited to them, and those other than thesilane coupling agents can be used if similar effects can be obtained.

Concretely, the treatment of pore surfaces refers to such treatment thata mesoporous silica film is immersed in an aimed silane coupling agent,However, the method of modification is not limited to this, and forexample, a method by which a reaction is caused in a gaseous phase isalso applicable.

When a coupling reaction is performed, a substance which acts as acatalyst for the reaction may be added.

The catalyst to be added is, for example, trimethylsilane.

Subsequently to the hydrophobicizing treatment of the interior of pores,a conjugated high molecular compound is introduced into the pores.

It is possible to use various conjugated polymers.

For example, it is possible to use those having a polyphenylene vynileneskeleton, those having a polythiophene skeleton, those having apolypyrrole skeleton, those having a polyfluorene skeleton and the like.However, conjugated polymers are not limited to them.

As methods of introducing a conjugated high molecular compound intopores, it is possible to adopt several methods, such as a method bywhich the above-described mesoporous silica film having a pore structurewhich is orientation controlled is immersed in a solution of aconjugated high molecular compound, and a method by which a conjugatedpolymer solution is caused to drop onto a substrate and heated.

In the present invention, any method may be used so long as it canintroduce a conjugated high molecular compound into pores.

In a case where a conjugated high molecular compound is introduced intopores by bringing the conjugated high molecular compound into contactwith a solution of a polymer solution, an excessive conjugated highmolecular material adheres to the outer surface of a film. Therefore, aprocess of removing this excessive conjugated high molecular material isperformed.

By performing the above-described steps, it is possible to prepare amesoporous silica film having tubular mesopores, which are uniaxiallyoriented and hold a conjugated high molecular compound in the pores, ona substrate.

The formation of a conjugated high molecular compound and theverification of orientation can be performed, for example, by thepolarized light measurement in an ultraviolet to visible ray absorptionanalysis.

Next, a thin film of the present invention is patterned in order to makethe structure of an element of the present invention.

Although the step of film patterning is described here after thepreparation of a film having oriented conjugated molecular chains, theorder of the process is not limited to this. For example, it is possibleto adopt such an order that a mesoporous film is patterned by thefollowing step, with a surfactant held within pores, and after that, astep of holding the above-described conjugated high molecular compoundis performed.

In a case where in the solvent evaporation method, a pattern is formedbeforehand by using the pen-lithography method and the ink jet method,the following patterning process is not always necessary.

A general method can be used in the patterning of a mesoporous film.

That is, a desired pattern can be formed by usual photolithography.

Concretely, a photoresist is applied to a film and exposure is performedby using a photomask for forming a desired film shape.

Next, after the development of the resist, the mesoporous film ispatterned by etching.

For example, in the case of a mesoporous silica film, it is possible toperform etching by using HF—NH₄F (buffered hydrofluoric acid).

Lastly, a patterned mesoporous film is obtained by removing the resist.

Next, two counter electrodes are prepared so that a magnetic field isapplied to this patterned mesoporous film having oriented tubularmesopores in the direction of the pores.

The arrangement is as shown in FIGS. 1 and 2.

Also in the preparation of the electrodes, a general lithography methodcan be used.

In the above-described patterning process, the most frequently usedmethod is such that with the resist not removed last, an electrodematerial is evaporated and after that, the evaporated metal is removedby a lift-off technique along with the above-described resist.

When a substrate having an electrically conductive part has also thefunction of the gate electrode as shown in FIG. 1, an electronic elementof the present invention can be fabricated by the above-describedprocess.

In the present invention, the conjugated polymer chains within a filmare electrically insulated by the pore walls of silica from the gateelectrode. However, as required, an insulating film may be separatelyformed.

When a gate electrode is formed in film form as shown in FIG. 2, anadditional process for preparing the gate electrode is necessary.

Also this gate electrode can be formed by using a generalphotolithography technique or a processing device which uses the focusedion beam process and the like.

Also in this case, because a conjugated high molecular compound iscovered with insulating pore walls, an electrode material can bedirectly formed.

The electronic element of the structure shown in FIG. 2 can befabricated by the above-described process.

When a voltage is applied to across electrodes formed at both ends of anoriented mesoporous film of this element, which holds a conjugated highmolecular compound in the pores, and an electric current observed ismeasured by changing the voltage applied to the gate electrode, areversibly changing condition of the current flowing across the twoelectrodes is observed as the potential in the gate electrode changesand it is ascertained that the electronic element of the presentinvention functions as a field-effect transistor.

The present invention will be described in further detail by usingembodiments. However, the present invention is not limited by thecontents of the embodiments.

Embodiment 1

This embodiment is an example in which an electronic elementschematically shown in FIG. 1 is fabricated by forming a mesoporoussilica film having oriented tubular mesopores on a highly doped siliconsubstrate which is coated with polyimide subjected to rubbing treatmentand by introducing polyhexyl thiophene into pores which have been madehollow by baking.

An NMP solution of polyamic acid A was applied to a clean p type silicon(100) substrate having resistivity of 0.01 Ωcm and baked at 200° C. for1 hour, whereby polyimide A having the following structure was formed.The film thickness of the polyimide A is 100 nm.

The polyimide was subjected to rubbing treatment under the conditionsshown in Table 1 and used as the substrate.

TABLE 1 Rubbing conditions for polyimide A Cloth material Nylon Rollerdiameter (mm) 24 Pressing depth (mm) 0.4 Number of revolutions (rpm)1000 Stage speed (mm/min) 600 Number of repetitions 2

A mesoporous silica film is formed on this substrate.

The surfactant used in this embodiment is polyoxyethylene-10-cetyl ethyl(abbreviated as C₁₆EO₁₀, trade name: Brij56), which is a nonionicsurfactant.

After this surfactant was dissolved in pure water, hydrochloric acid andtetraethoxysilane were added so that the mole ratio of each component ina final solution became as follows:TEOS:H₂O:HCl:C₁₆EO₁₀=0.10:100:3.0:0.10.

The substrate coated with the above-described rubbing treated polyimidewas held in this solution, with the substrate surface facing downward,at 80° C. for three days, and a mesoporous silica film was prepared.

The substrate taken out of the reaction solution was thoroughly cleanedwith pure water and then air dried.

Upon the substrate, a transparent film was formed and a uniforminterference color was observed.

This film was measured by an X-ray diffraction analysis and as a result,it was ascertained that the film has a 5.1 nm cyclic structure in thedirection of the film thickness.

A section of this film was observed under a transmission electronmicroscope and as a result, it became apparent that in this film,tubular mesopores have a honeycomb packing structure.

Next, an in-plane X-ray diffraction analysis of this film was tried.

As a result, it was confirmed that the film has a 7.4 nm cyclicstructure in the plane.

For the structure which gives this diffraction peak, an in-plane rockingcurve was measured in order to investigate an orientation distributionin the plane.

As a result, two diffraction peaks at intervals of 180° were observed.It became apparent from this result that in the mesoporous silica filmprepared in this embodiment, tubular pores are oriented in onedirection.

The orientation direction was perpendicular to the direction of rubbingtreatment.

The uniaxial orientation of the tubular mesopores was ascertained alsoby use of a transmission electron microscope, and it was ascertainedthat the pores are completely orientation controlled throughout the filmwith respect to the film thickness direction.

Next, this film was patterned. The patterning size is a rectangle 3 μmin width×200 μm in length.

First, a positive resist AZ-1500 was applied to the film underprescribed conditions, with the surfactant held in the pores, andexposure was performed by use of a photomask made in order to form apattern of the above-described size.

The photoresist was developed and a resist pattern was prepared on thefilm.

As a result of an observation under an optical microscope, it was foundthat the same resist pattern as the pattern of the photomask had beenformed on the film.

This resist pattern is schematically shown in FIG. 5B.

Next, the etching of the mesoporous silica film was performed by usingthis resist pattern as a mask (FIG. 5C).

The etching was performed by using a buffer solution of hydrofluoricacid (NH₄F+HF; HF:NH₄F=1:5).

It was ascertained that the mesoporous silica film is completely removedby etching for 30 seconds.

After the buffer solution of hydrofluoric acid was thoroughly cleanedand removed, this film was dried at 60° C. and an electrode metal wasevaporated on the whole surface by the sputtering method (FIG. 5D).

In the evaporation step of the electrode metal, titanium is firstevaporated in a film thickness of 5 nm and platinum is then evaporatedin a film thickness of 300 nm.

After the completion of the evaporation of the electrode, thephotoresist and the electrode material formed thereon were removed by alift-off technique (FIG. 5F).

Because in this condition the surfactant is held in the pores, it isnecessary to remove the surfactant before the introduction of aconjugated high molecular compound.

For this purpose, the film after the patterning was baked at 500° C. forfive hours.

In this step, the polyimide film on the substrate is removed and asilicon oxide film which functions as a gate insulating film is formedon the silicon substrate.

The mesoporous silica film was patterned with a desired size asdescribed above.

It was ascertained by an X-ray diffraction analysis that also after thispatterning process, the structural regularity of mesoporous silica ismaintained.

In order to obtain information on the pore diameter of this film, thefilm was baked, the surfactant was removed from the interior of thepores, and an adsorption isothermal curve of nitrogen gas was measured.

As a result, the adsorption showed a type IV behavior.

This result was analyzed by the Barrett-Joyner-Halenda (BJH) method andit was found that the pore diameter distribution of the mesoporoussilica film prepared in this embodiment is a narrow distribution havinga single peak at 3.2 nm and that not less than 80% of the pores are in a10 nm distribution.

This can be ascertained also in a mesoporous film which is notpatterned.

This mesoporous silica film for which a hollow pore structure has beenmade by baking is first subjected to silane coupling treatment, wherebythe surfaces of the pores are hydrophobicized.

Concretely, the film immediately after the baking was immersed in amixture of trimethyl-chlorosilane and 1,1,1,3,3,3-hexamethyl-disilazanat a ratio of 1:1 for 2 hours, cleaned with ethanol to remove anexcessive silane coupling agent, and then dried.

Subsequently to this, a conjugated high molecular compound is introducedinto the pores.

The conjugated high molecular compound introduced in this embodiment is9.9-dioctylfluorene-co-bithiophene, which is known as F8T2.

Then 0.3 g of F8T2 was dissolved in 10 ml of chlorobenzene, and theabove-described oriented mesoporous silica film was held in thissolution at 80° C. for 3 days.

After that, the mesoporous silica film was taken out of the solution andexcessive F8T2 adhering to the external surface was cleaned withchloroform and removed, and the mesoporous silica film was dried at roomtemperature.

F8T2 could be introduced into the pores by the process described above.

This can be ascertained by measuring the polarized absorption spectrumof the film after the introduction of F8T2 in thereflection/transmission mode.

That is, the F8T2 which is held in the oriented pores shows a strongabsorption-polarization dependence, and absorption derived from theconjugated high molecular compound was observed only when the directionof polarization was parallel to the orientation direction of the pores.

This shows that the molecular chains of the conjugated high molecularcompound are orientation controlled in one direction by the pores ofhigh anisotropy.

An element of the structure schematically shown in FIG. 1 was fabricatedby the process described above.

In this element, by applying a voltage across electrodes formed at bothends of the film, a current flowing across the electrodes was measured,with a voltage applied to the substrate functioning as the gateelectrode being changed.

As a result, the current across the electrodes was observed to behave soas to increase with increasing voltage which is applied to thesubstrate, and it was ascertained that the electronic element fabricatedin this embodiment functions as a field-effect transistor.

Embodiment 2

This embodiment is an example in which as with Embodiment 1, by use of asubstrate which is coated with a polyimide film subjected to rubbingtreated, a mesoporous silica film, the pore direction of which isorientation controlled in one direction on the substrate, is prepared bydip coating based on the sol-gel method and after the introduction ofpolyhexyl thiophene into the pores, each electrode for the source, drainand gate is formed by the focused ion beam (FIB) process and afield-effect transistor is fabricated.

Polyamic acid A, which is the same precursor solution of polyimide A asused in Embodiment 1, is applied to a quartz glass substrate which hasbeen thoroughly cleaned with acetone, isopropyl alcohol and pure waterand the surface of which has been UV/ozone treated, and a polyimide filmwas formed by the same heat treatment as in Embodiment 1.

This substrate was subjected to rubbing treatment by use of the sameapparatus as with Embodiment 1 under the same conditions as inEmbodiment, and used as the substrate for preparing a mesoporous silicafilm.

A mesoporous silica film is formed on this substrate by the dip coatingmethod.

Also in this embodiment, C₁₆EO₁₀, the same surfactant as in Embodiment1, was used in preparing the mesoporous silica film.

The composition of the precursor solution which was used was adjusted soas to obtain: C₁₆EO₁₀ 0.08:TEOS 1.0:EtOH 22:H₂O 5:HCl 0.004.

The above-described substrate was immersed in this precursor solutionand drawn up at a speed of 3 mm/sec.

This film was held in an atmosphere of 40° C. to 50% for 24 hours and amesoporous silica film which holds the surfactant in pores was prepared.

A uniform film was formed on the substrate and a uniform interferencecolor was observed.

This film was measured by an X-ray diffraction analysis and as a result,it was ascertained that the film has a 4.6 nm cyclic structure in thedirection of the film thickness.

A section of this film was observed under a transmission electronmicroscope and as a result, it became apparent that in this film,tubular mesopores have a honeycomb packing structure.

An in-plane X-ray diffraction analysis of this film was tried. As aresult, it was confirmed that the film has a 7.2 nm cyclic structure inthe plane.

For the structure which gives this diffraction peak, an in-plane rockingcurve was measured in order to investigate an orientation distributionin the plane.

As a result, two diffraction peaks at intervals of 180° were observed.It became apparent from this result that in the mesoporous silica filmprepared in this embodiment, tubular pores are oriented in onedirection.

The half-width of the peaks of the in-plane rocking curve was smallerthan in the film prepared in Embodiment 1 and it became apparent thatthe orientation distribution in the plane is narrow.

The orientation direction was perpendicular to the direction of rubbingtreatment, and this is the same as in the case of the mesoporous silicafilm of Embodiment 1.

The uniaxial orientation of the tubular mesopores was ascertained alsoby use of a transmission electron microscope, and it was ascertainedthat the pores are completely orientation controlled throughout the filmwith respect to the film thickness direction.

In order to obtain information on the pore diameter of this film, thefilm was baked at 500° C. for six hours, the surfactant was removed frominside the pores, and an adsorption isothermal curve of nitrogen gas wasmeasured.

As a result, the adsorption showed a type IV behavior.

This result was analyzed by the BJH method and it was found that thepore diameter distribution of the mesoporous silica film prepared inthis embodiment is a narrow distribution having a single peak at 3.0 nmand that not less than 80% of the pores are in a 10 nm distribution.

It has been ascertained that in this film, the pore structure in theplane does not change although the shrinkage of the structure occurs inthe film thickness direction due to baking.

The degree of shrinkage in the in-plane direction was greater than withthe film prepared in Embodiment 1.

Subsequently, this film was treated with a silane coupling agent underthe same conditions as described in Embodiment 1 and the inner walls ofthe pores were hydrophobicized.

Next, poly-3-hexylthiophene, which is a conjugated high molecularcompound, is introduced into the pores of the oriented mesoporous silicawhich has been hydrophobicized.

Then 0.3 g of poly-3-hexylthiophene was dissolved in 10 ml ofchlorobenzene, and the above-described oriented mesoporous silica filmwas held in this solution at 80° C. for 3 days.

After that, the mesoporous silica film was taken out of the solution andexcessive poly-3-hexylthiophene adhering to the external surface wascleaned with chloroform and removed, and the mesoporous silica film wasdried at room temperature.

Although the mesoporous silica film after the introduction ofpoly-3-hexylthiophene was colored in dark purple, the transparency andthe like of the film was maintained.

Poly-3-hexylthiophene could be introduced into the oriented mesoporoussilica pores prepared by dip coating in this embodiment by the processdescribed above.

This can be ascertained by measuring the polarized absorption spectrumof the film after the introduction of poly-3-hexylthiophene.

That is, the poly-3-hexylthiophene which is held in the oriented poresshows a strong absorption-polarization dependence, and absorptionderived from the conjugated high molecular compound was observed onlywhen the direction of polarization was parallel to the orientationdirection of the pores.

This shows that the molecular chains of the conjugated high molecularcompound are orientation controlled in one direction by the pores ofhigh anisotropy.

Next, this film was patterned with the same shape as in Embodiment 1 bythe same method described in Embodiment 1 (FIGS. 6A to 6C).

In this embodiment, however, the photoresist was removed after theremoval of the mesoporous silica film by etching (FIG. 6D).

Subsequently to this, an electrode material was formed on the wholesurface of the element as shown in FIG. 6E

The film formation of the electrode material was performed by thesputtering method, and platinum was evaporated in a film thickness of300 nm after the evaporation of titanium in a film thickness of 5 nm.

Lastly, as shown in FIG. 6F, in order to separate electrodes performingthe functions of the gate, source and drain, processing was performed byusing the focused ion beam (FIB) process.

In this case, the poly-3-hexylthiophene in the mesoporous silica poresis electrically separated from the gate electrode by the insulating porewalls of mesoporous silica and, therefore, it is unnecessary to providea gate insulating film. However, an insulating film which is not shownin the figure may be formed.

The element of the structure schematically shown in FIG. 2 wasfabricated by the process described above.

In this element, by applying a voltage across electrodes formed at bothends of the film, a current flowing across the electrodes was measured,with a voltage applied to the gate electrode being changed.

As a result, the current across the electrodes was observed to behave soas to increase with increasing voltage which is applied to the gateelectrode, and it was ascertained that the electronic element fabricatedin this embodiment functions as a field-effect transistor.

Embodiment 3

This embodiment is an example in which, by use of a surfactant having apolymerizing part, a mesoporous silica film having uniaxially orientedtubular mesopores is prepared on a low-resistivity silicon substrateused in Embodiment 1, on which a polyimide film subjected to rubbingtreated is formed, an oriented conjugated high molecular compound isprepared in pores by the polymerization of the surfactant in the pores,after that, this film is patterned and electrodes are formed, whereby anelectronic element of the structure shown in FIG. 2 is fabricated.

First, in the same procedure as in Embodiment 1, a film of polyimide Awas formed on the substrate and subjected to rubbing treatment under thesame conditions as in Embodiment 1.

A surfactant having a diacetylene part of the structureC₁₁H₂₃—C≡C—C≡CH₂—N⁺(CH₃)₃ as a polymerizable part was synthesized, andan oriented mesoporous silica film was prepared by using this surfactantin a template.

The preparation of the mesoporous silica film was performed by themethod based on nonuniform nucleation-nucleus growth as in Embodiment 1.

After the above-described surfactant was dissolved in pure water,hydrochloric acid and tetraethoxysilane were added so that the moleratio of each component in a final solution became as follows:TEOS:H₂O:HCl:surfactant=0.125:100:8.0:0.10.

The substrate coated with the above-described rubbing treated polyimidewas held in this solution, with the substrate surface facing downward,at 80° C. for three days, and a mesoporous silica film was prepared.

The substrate taken out of the reaction solution was thoroughly cleanedwith pure water and then air dried.

Upon the substrate, a transparent film was formed and a uniforminterference color was observed.

This film was measured by an X-ray diffraction analysis and as a result,it was ascertained that the film has a 3.5 nm cyclic structure in thedirection of the film thickness.

A section of this film was observed under a transmission electronmicroscope and as a result, it became apparent that in this film,tubular mesopores have a honeycomb packing structure.

Also for this film, an in-plane X-ray diffraction analysis was tried. Anin-line rocking curve was measured for observed in-plane X-raydiffraction peaks. As a result, two diffraction peaks at intervals of180° were observed. It became apparent from this result that in themesoporous silica film prepared in this embodiment, tubular pores areoriented in one direction.

The orientation direction was perpendicular to the direction of rubbingtreatment.

The uniaxial orientation of the tubular mesopores was ascertained alsoby use of a transmission electron microscope, and it was ascertainedthat the pores are completely orientation controlled throughout the filmwith respect to the film thickness direction.

Next, this film was annealed and the surfactant held in the pores waspolymerized.

As a result, the diacetylene part of the surfactant is polymerized,thereby forming a conjugated high molecular compound in the pores.

The confirmation of the polymerization was performed based on the factthat in an infrared absorption spectrum, an absorption peak of 2260 cm⁻¹ascribed to the stretching vibration of a carbon-carbon triple bonddisappears after the annealing.

The polarized absorption spectrum of the film after the polymerizationwas measured. As a result, absorption was observed only when thedirection of polarization is parallel to the orientation direction ofthe pores, and it was ascertained that polymer chains are oriented inthe pores.

This polymerization is schematically shown in FIGS. 7A and 7B.

The conjugated high molecular compound in which the surfactant ispolymerized is oriented in the pores.

Next, this film was patterned by the same process as in Embodiment 1,and electrodes were formed. However, the removal of the photoresist wasperformed by using isopropyl alcohol.

In this case, as in Embodiment 1, the silicon gate has the function ofthe gate electrode.

An element of the structure schematically shown in FIG. 2 was fabricatedby the above-described process.

In this element, by applying a voltage across electrodes formed at bothends of the film, a current flowing across the electrodes was measured,with a voltage applied to the substrate functioning as the gateelectrode being changed.

As a result, the current across the electrodes was observed to behave soas to increase with increasing voltage which is applied to thesubstrate, and it was ascertained that the electronic element fabricatedin this embodiment functions as a field-effect transistor.

Although the mode of this embodiment is limited to a transistor, thepresent invention is not limited to this. For example, if theconfiguration of a transistor is such that changes in gate potential canbe monitored as a current across the source and the drain when asubstance has been adsorbed in the gate portion, then it is alsopossible to use the element as a sensor.

It might be thought that the transistor could be used in generalapplications.

The present invention relates to a novel organic semiconductor elementwhich utilizes the main-chain transmission of a conjugated highmolecular compound which is orientation controlled at a molecular level.

This application claims priority from Japanese Patent Application No.2005-152465 filed May 25, 2005, which is hereby incorporated byreference herein.

1-7. (canceled)
 8. A method of manufacturing an electronic elementcomprising a pair of electrodes formed on a substrate, a mesoporous filmhaving tubular mesopores oriented in one direction, the mesoporous filmbeing formed between the pair of electrodes so as to be in contact withthe pair of electrodes, a conjugated high molecular compound held in thetubular mesopores, and a third electrode which is electrically insulatedfrom the conjugated high molecular compound and formed so as to be incontact with the mesoporous film, the method comprising a step offorming the conjugated high molecular compound in the tubular mesopores,which step comprises: a step of forming the mesoporous film which ismade up so as to contain tubular molecular assemblies of a surfactanthaving a uniform diameter, which are oriented in one direction; a stepof removing the surfactant from the tubular mesopores of the mesoporousfilm; a step of performing treatment so that pore surfaces of thetubular mesopores after removal of the surfactant obtain hydrophobicity;and a step of introducing the conjugated high molecular compoundsubsequently to the hydrophobicizing treatment.
 9. A method ofmanufacturing an electronic element comprising a pair of electrodesformed on a substrate, a mesoporous film having tubular mesoporesoriented in one direction, the mesoporous film being formed between thepair of electrodes so as to be in contact with the pair of electrodes, aconjugated high molecular compound held in the tubular mesopores, and athird electrode which is electrically insulated from the conjugated highmolecular compound and formed so as to be in contact with the mesoporousfilm, the method comprising a step of forming the conjugated highmolecular compound in the tubular mesopores, which step comprises: astep of forming the mesoporous film which is made up so as to containtubular molecular assemblies of a surfactant having a uniform diameter,which are aligned in one direction, by use of a surfactant having afunctional group capable of forming the conjugated high molecularcompound by polymerization; and a step of forming the conjugated highmolecular compound by causing the surfactant in the mesoporous film topolymerize. 10-11. (canceled)
 12. The method according to claim 8,wherein the orientation direction of the tubular mesopores is parallelto the direction of an electric field when an electrical potential isapplied across the pair of electrodes.
 13. The method according to claim8, wherein the electronic element is a field-effect transistor whichcontrols the amount of a current flowing across the pair of electrodesby an electrical potential applied to the third electrode.
 14. Themethod according to claim 13, wherein a material for the mesoporous filmis silica.
 15. The method according to claim 13, wherein a material forthe mesoporous film is a hybrid material of silica and an organicsubstance.
 16. The method according to claim 8, wherein a material forthe mesoporous film contains a silicon oxide.
 17. The method accordingto claim 8, wherein at least a portion of the substrate is a substratehaving electrical conductivity and the substrate serves also as thethird electrode.
 18. The method according to claim 9, wherein theorientation direction of the tubular mesopores is parallel to thedirection of an electric field when an electrical potential is appliedacross the pair of electrodes.
 19. The method according to claim 9,wherein the electronic element is a field-effect transistor whichcontrols the amount of a current flowing across the pair of electrodesby an electrical potential applied to the third electrode.
 20. Theelectronic element according to claim 19, wherein a material for themesoporous film is silica.
 21. The electronic element according to claim19, wherein a material for the mesoporous film is a hybrid material ofsilica and an organic substance.
 22. The electronic element according toclaim 9, wherein a material for the mesoporous film contains a siliconoxide.
 23. The electronic element according to claim 9, wherein at leasta portion of the substrate is a substrate having electrical conductivityand the substrate serves also as the third electrode.